Liquid absorbent base web

ABSTRACT

The present invention is generally directed to base webs that are creped after a bonding material has been applied to at least one side of the web according to a predetermined pattern. The base web disclosed in the present application is made from at least three fibrous layers. The outer layers of the web contain synthetic staple fibers for increasing the tensile strength and abrasion resistant properties of the web. In one embodiment, the middle layer can further contain hardwood fibers, such as eucalyptus fibers, which improves the wipe dry properties of the web.

FIELD OF THE INVENTION

[0001] The present invention is generally directed to abrasion resistantand strong base webs that have good liquid absorption properties. Thebase web is generally made from a combination of pulp fibers andsynthetic fibers. In one embodiment, the base web is used as a wipingproduct.

BACKGROUND OF THE INVENTION

[0002] Liquid absorbent products such a paper towels, industrial wipers,food service wipers, napkins, medical pads, and other similar productsare designed to include several important properties. For example, theproducts should have good bulk, a soft feel and should be highlyabsorbent. The products should also have good strength even when wet andshould resist tearing. Further, the products should also have goodstretch characteristics, should be abrasion resistant, and should notdeteriorate in the environment in which they are used.

[0003] In the past, many attempts have been made to enhance and increasecertain physical properties of such products. Unfortunately, however,when steps are taken to increase one property of these products, othercharacteristics of the products may be adversely affected. For instance,the softness of paper wiping products can be increased by severaldifferent methods, such as by selecting a particular fiber type, or byreducing cellulosic fiber bonding within the product. Increasingsoftness according to one of the above methods, however, may adverselyaffect the strength of the product. Conversely, steps normally taken toincrease the strength of a fibrous web typically have an adverse impactupon the softness or the absorbency of the web.

[0004] One particular process that has proven to be very successful inproducing paper towels and other wiping products is disclosed in U.S.Pat. No. 3,879,257 to Gentile, et al., which is incorporated herein byreference in its entirety. In Gentile, et al., a process is disclosedfor producing soft, absorbent, single ply fibrous webs having alaminate-like structure that are particularly well suited for use aswiping products.

[0005] The fibrous webs disclosed in Gentile, et al. are formed from anaqueous slurry of principally lignocellulosic fibers under conditionswhich reduce inner fiber bonding. A bonding material, such as a latexelastomeric composition, is applied to a first surface of the web in aspaced-apart pattern. In particular, the bonding material is applied sothat it covers from about 50% to about 60% of the surface area of theweb. The bonding material provides strength to the web and abrasionresistance to the surface. Once applied, the bonding material canpenetrate the web preferably from about 10% to about 40% of thethickness of the web.

[0006] The bonding material can then be similarly applied to theopposite side of the web for further providing additional strength andabrasion resistance. Once the bonding material is applied to the secondside of the web, the web can be brought into contact with a crepingsurface. Specifically, the web will adhere to the creping surfaceaccording to the pattern to which the bonding material was applied. Theweb is then creped from the creping surface with a doctor blade. Crepingthe web greatly disrupts the fibers within the web, thereby increasingthe softness, absorbency, and bulk of the web.

[0007] In one of the preferred embodiments disclosed in Gentile. et al.,both sides of the paper web are creped after the bonding material hasbeen applied. Gentile. et al. also discusses the use of chemicaldebonders to treat the fibers prior to forming the web in order tofurther reduce innerfiber bonding and to increase softness and bulk.

[0008] Although the processes disclosed in Gentile. et al. have providedgreat advancements in the art of making disposable wiping products, thepresent invention is directed to further improvements in fibrous basewebs. In particular, the present invention is directed to a fibrous baseweb having an improved combination of abrasion resistance, strength, andwipe dry properties. These and other advantages will be made apparentfrom the following description.

SUMMARY OF THE INVENTION

[0009] As stated above, the present invention is directed to furtherimprovements in prior art constructions and methods, which are achievedby providing an abrasion resistant, liquid absorbent base web. The baseweb may include a first outer fibrous layer defining a first side of theweb and a second and opposing outer fibrous layer defining a second sideof the web. The first and second outer layers may contain syntheticstaple fibers either alone or in combination with pulp fibers. Anintermediate fibrous layer may be positioned between the first outerlayer and the second outer layer. The intermediate layer may containpulp fibers.

[0010] Desirably, a bonding material is applied to at least one side ofthe base web. In particular, the bonding material may be applied to theweb according to a predetermined pattern, such as a geometric pattern.After the bonding material is applied to at least one side of the web,the web may be creped. For instance, in one embodiment, the bondingmaterial may be applied to both sides of the base web and both sides ofthe web may then be creped.

[0011] The synthetic staple fibers contained within the base web of thepresent invention can be made from one or more polymers includingpolyester, nylon, polypropylene and rayon. The fibers can have a lengthof at least 0.25 inches and can have a denier of less than about 2.5,and particularly less than 1.5. The synthetic fibers can be added to thebase web in an amount up to about 50% by weight and particularly fromabout 5% to about 15% by weight. Further, each outer layer containingthe synthetic fibers can comprise from about 15% to about 40% of thetotal weight of the web, and particularly from about 25% to about 35% ofthe weight of the web.

[0012] In order to increase softness and the liquid absorbent propertiesof the base web, the intermediate fibrous layer can contain short pulpfibers having a low coarseness, which create a pore size gradientbetween the outer layers and the inner layer. It is believed that bycreating a pore size gradient, the base web has improved wickingproperties. Short fibers having a low coarseness that may be included inthe intermediate layer include hardwood fibers, such as eucalyptusfibers or eucalyptus-like fibers. For instance, the fibers can have alength of less than about 2.0 millimeters and a coarseness of less thanabout 10. The hardwood fibers can be present within the base web in anamount from about 10% to about 40% by weight.

[0013] Other fibers that may be incorporated into the intermediatefibrous layer in order to improve the wipe dry properties of the baseweb include highly liquid absorbent and highly wettable fibers. Forinstance, such fibers can include highly extracted pulp fibers, such asmercerized alpha pulp fibers. The alpha pulp can be made from softwoodfibers or hardwood fibers and can be present in the intermediate layereither alone or in combination with the above-described fibers.

[0014] The bonding material applied to the base web can be applied in apattern that covers from about 10% to about 60%, and more particularlyfrom about 20% to about 50% of the surface area of each side of the web.The bonding material can be applied to each side of the web in an amountup to about 10% by weight, and particularly from about 5% to about 8% byweight. Once applied, the bonding material can penetrate the web in anamount from about 15% to about 50% of the total thickness of the web.

[0015] The preselected pattern used to apply the bonding material canbe, in one embodiment, a reticular interconnected design. Alternatively,the preselected pattern can comprise a succession of discrete dots. Thebonding material can be for instance, a latex, such as an ethylene vinylacetate copolymer cross-linked with N-methyl acrylamide groups.Copolymers of vinyl acrylics with cross-linking capability are alsouseful.

[0016] Once formed, the base web of the present invention can have abasis weight of from about 20 pounds per ream to about 80 pounds perream, depending upon the particular application. The base web can beused in numerous products. For instance, the base web can be used as awiping product, as a napkin, as a medical pad, as a placemat, as a covermaterial such as a car cover, as a paint drop cloth, as one layer in alaminate product or as any other similar liquid absorbent product.

[0017] These and other features are also achieved by providing a methodfor producing a base web. The method may include first providing afibrous web having a middle layer containing pulp fibers, such ashardwood fibers. The base web may further include a first outer layercontaining synthetic staple fibers and a second outer layer alsocontaining synthetic staple fibers. The synthetic staple fibers may bepresent within the outer layers either alone or in combination with pulpfibers.

[0018] A first bonding material may be applied to the first side of theweb in a preselected pattern and, if desired, a second bonding materialmay be applied to the second side of the web also in a preselectedpattern. Once the bonding materials are applied to the web, the web maythen be crepes. For instance, the web can be adhered to a crepingsurface and then creped from the surface using, for instance, a crepingblade.

[0019] Other features and aspects of the present invention are discussedin greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A full and enabling disclosure of the present invention,including the best mode thereof to one of ordinary skill in the art, isset forth more particularly in the remainder of the specification,including reference to the accompanying figures in which:

[0021]FIG. 1 is a schematic diagram of a fibrous web forming machineillustrating one embodiment for forming a base web having multiplelayers in accordance with the present invention;

[0022]FIG. 2 is a schematic diagram of a fibrous web forming machinethat crepes one side of the web; and

[0023]FIG. 3 is a schematic diagram of one embodiment of a system fordouble creping a base web in accordance with the present invention.

[0024] Repeat use of reference characters in the present specificationand drawings is intended to represent same or analogous features orelements of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] It is to be understood by one of ordinary skill in the art thatthe present discussion is a description of exemplary embodiments only,and is not intended as limiting the broader aspects of the presentinvention, which broader aspects are embodied in the exemplaryconstruction.

[0026] In general, the present invention is directed to a strong andabrasion resistant base web. Of particular advantage, in one embodiment,the base web is made with improved strength while maintaining goodsoftness characteristics and liquid absorbency properties. Inparticular, the base web contains an extremely efficient wickingmechanism which transports fluid from the surface of the base web intothe interior of the web. Further, the base web has good stretchcharacteristics, is tear-resistant and does not produce a substantialamount of lint when in use.

[0027] The base web of the present invention may have a multi-layerconstruction. In particular, the web may be made from a stratified fiberfurnish having three principal layers. In accordance with the presentinvention, the outer layers of the web contain staple synthetic fibers,such as polymeric fibers. The synthetic fibers in the outer layers ofthe web make the web resistant to surface abrasion and reinforce thetensile strength properties of the web.

[0028] In one embodiment, the base web can also include an intermediatelayer containing relatively short fibers that have a low coarsenessvalue or other highly wettable and absorbent fibers. For instance, theintermediate layer can contain hardwood fibers, such as eucalyptusfibers or eucalyptus-like fibers. The hardwood fibers contained withinthe intermediate layer create a pore and capillary size gradient betweenthe outer layers and the intermediate layer. This pore and capillarysize gradient increases the wicking properties of the base web,providing the web with enhanced liquid absorbent properties. Theintermediate layer of the web counteracts the hydrophobicity of thesynthetic fibers causing fluids contacting the web to be transportedinto the interior of the web. Further, since the hardwood fibers arecontained in the intermediate layer, the base web does not create asubstantial amount of lint when in use.

[0029] The base web of the present invention may further include abonding material that is applied to at least one side of the web, anddesirably to both sides of the web. After the bonding material isapplied, the web may be creped at least on one side and preferably onboth sides. More particularly, the bonding material may be applied tothe web in a preselected pattern for providing strength andstretchability without adversely affecting the softness of the web.Creping the web increases the softness and bulk of the web.

[0030] As stated above, one aspect of the present invention is directedto incorporating into the outer layers of the base web synthetic staplefibers. As used herein, synthetic staple fibers refer to fibers madefrom one or more synthetic materials, such as polymeric materials, andcan include single component and multi-component fibers, such asbicomponent fibers. Bicomponent fibers refer to fibers made from twodistinct polymers such as in a side-by-side arrangement or in a core andsheath arrangement. Particular materials which may be used to constructthe synthetic fibers include nylon, polypropylene, and rayon. In onepreferred embodiment, polyester fibers are used.

[0031] In general, the length and the denier of the synthetic fiberswill depend upon the particular application and the manner in which thebase web is formed. For most applications, the fibers should have alength of at least 0.25 inches, such as from about 0.25 inches to about0.75 inches. Longer fibers, which may enhance the strength of the web,however, may be used.

[0032] The denier of the fibers, on the other hand, is preferablyrelatively low. For instance, the denier of the fibers can be less thanabout 2.5 dpf, and particularly less than about 1.5 dpf. By usingsmaller denier fibers, less material may be needed in forming the web.

[0033] The synthetic staple fibers should be incorporated into the outerlayers of the web in an amount sufficient to increase the abrasionresistance and the tensile strength properties of the web. The amount ofsynthetic fibers added to the web will also generally depend upon theparticular application. In most embodiments, the synthetic fibers can bepresent within the web in an amount up to about 50% by weight, andparticularly from about 5% to about 15% by weight. Further, for mostapplications, the amount of synthetic fibers contained within one of theouter layers of the base web will be substantially equal to the amountof synthetic fibers contained within the opposing outer layer of thebase web.

[0034] The weight of each outer layer in relation to the total weight ofthe web is generally not critical. In most embodiments, however, theweight of each outer layer will be from about 15% to about 40% of thetotal weight of the web, and particularly from about 25% to about 35% ofthe weight of the web.

[0035] Besides synthetic staple fibers, the outer layers can alsocontain pulp fibers, such as various cellulosic fibers. For example, inone embodiment, Northern softwood kraft fibers can be combined with thesynthetic fibers. Softwood fibers generally have a fiber length of fromabout 1.8 millimeters to about 3 millimeters. Preferably, the pulpfibers are mixed homogeneously with the synthetic staple fibers.

[0036] The middle layer of the base web of the present invention cancontain various types of fibers. In one preferred embodiment, the middlelayer contains hardwood fibers either alone or in combination withsoftwood fibers. In particular, hardwood fibers can be added to themiddle layer so as to create a pore and capillary size gradient betweenthe outer layers and the middle layer, which creates a highly efficientwicking mechanism as described above.

[0037] More particularly, the hardwood fibers incorporated into themiddle layer of the base web should have a relatively short fiber lengthand a relatively low coarseness rating, which serve to create the poresize gradient described above. For instance, the hardwood fibers canhave a length of less than about 2 millimeters, and particularly lessthan about 1.5 millimeters. The coarseness rating of the fibers, on theother hand, can be less than 10, and particularly less than 8, asdetermined on a KAJANNI fiber testing machine.

[0038] In one embodiment, the hardwood fibers incorporated into themiddle layer of the base web include eucalyptus fibers. Eucalyptusfibers typically have a length of from about 0.8 millimeters to about1.2 millimeters. When added to the web, eucalyptus fibers increase thesoftness, enhance the brightness, increase the opacity, and increase thewicking ability of the web.

[0039] Besides eucalyptus fibers, other eucalyptus-like fibers may alsobe incorporated into the base web of the present invention. As usedherein, eucalyptus-like fibers refer to fibers that have similarcharacteristics to eucalyptus fibers. Such fibers include, for instance,birch fibers and possibly recycled wood fibers.

[0040] Besides the above-described hardwood fibers, other fibersparticularly well-suited for use in the middle layer of the base web arehighly absorbent and wettable fibers, such as those produced when woodpulp is highly extracted. For instance, mercerized alpha pulp may beincorporated into the base web. Alpha pulp can contain softwood fibersor hardwood fibers. Since alpha pulp is highly wettable, the pulp willincrease the wipe dry properties of the base web similar to eucalyptusfibers. Alpha pulp is commercially available from, for instance, ITRayonier.

[0041] In general, the above-described hardwood fibers or alpha pulp canbe present in the base web in an amount from about 10% to about 40% byweight and particularly in an amount of about 20% by weight. The fiberscan comprise from about 5% to about 100% by weight of the middle layerof the web.

[0042] As stated above, the hardwood fibers or alpha pulp fibers can bepresent within the middle layer of the web either alone or incombination with other fibers, such as other cellulosic fibers. Forinstance, the hardwood fibers can be combined with softwood fibers, withrecycled fibers, with superabsorbent materials, and withthermomechanical pulp. Besides fibers, any material that may enhance aproperty of the base web may also be included within the middle layer.

[0043] The multi-layered base web made according to the process of thepresent invention, for most applications, should be formed without asubstantial amount of inner fiber-to-fiber bond strength. In thisregard, the fiber furnish used to form the base web can be treated witha chemical debonding agent. The debonding agent can be added to thefiber slurry during the pulping process or can be added directly intothe head box. Suitable debonding agents that may be used in the presentinvention include cationic debonding agents such as fatty dialkylquaternary amine salts, mono fatty alkyl tertiary amine salts, primaryamine salts, imidazoline quaternary salts, and unsaturated fatty alkylamine salts. Other suitable debonding agents are disclosed in U.S. Pat.No. 5,529,665 to Kaun which is incorporated herein by reference.

[0044] In one preferred embodiment, the debonding agent used in theprocess of the present invention can be an organic quaternary ammoniumchloride. In this embodiment, the debonding agent can be added to thefiber slurry in an amount from about 0.1% to about 1% by weight, basedon the total weight of fibers present within the slurry.

[0045] The manner in which the base web of the present invention isformed may vary depending upon the particular application. For instance,in one embodiment, the web can be formed in a wet lay process accordingto conventional paper making techniques. In a wet lay process, the fiberfurnish is combined with water to form an aqueous suspension. Theaqueous suspension is spread onto a wire or felt and dried to form theweb.

[0046] Alternatively, the base web of the present invention can be airformed. In this embodiment, air is used to transport the fibers and forma web. Air forming processes are typically capable of processing longerfibers than most wet lay processes, which may provide an advantage insome applications.

[0047] Referring to FIGS. 1-3, one embodiment of a process for producinga base web in accordance with the present invention is illustrated. Theprocess illustrated in the figures depicts a wet lay process, although,as described above, other techniques for forming the base web of thepresent invention may be used.

[0048] Referring to FIG. 1, one embodiment of a device for forming amulti-layered stratified fiber furnish is illustrated. As shown, athree-layered head box generally 10 may include an upper head box wall12 and a lower head box wall 14. Head box 10 may further include a firstdivider 16 and a second divider 18, which separate three fiber stocklayers.

[0049] Each of the fiber layers comprise a dilute aqueous suspension offibers. In accordance with the present invention, as described above,middle layer 20 can contain hardwood fibers, softwood fibers or acombination of both. Outer layers 22 and 24, on the other hand, containsynthetic staple fibers alone or in combination with pulp fibers, suchas softwood fibers.

[0050] An endless traveling forming fabric 26, suitably supported anddriven by rolls 28 and 30, receives the layered stock issuing from headbox 10. Once retained on fabric 26, the layered fiber suspension passeswater through the fabric as shown by the arrows 32. Water removal isachieved by combinations of gravity, centrifugal force and vacuumsuction depending on the forming configuration.

[0051] Forming multi-layered webs is also described and disclosed inU.S. Pat. No. 5,129,988 to Farrington, Jr. and in U.S. Pat. No.5,494,554 to Edwards, et al., which are both incorporated herein byreference.

[0052] Referring to FIG. 2, one embodiment of a base web forming machineis illustrated capable of receiving the layered fiber suspension fromhead box 10 and forming a web. As shown, in this embodiment, formingfabric 26 is supported and driven by a plurality of guide rolls 34. Avacuum box 36 is disposed beneath forming fabric 26 and is adapted toremove water from the fiber furnish to assist in forming a web.

[0053] From forming fabric 26, a formed web 38 is transferred to asecond fabric 40, which may be either a wire or a felt. Fabric 40 issupported for movement around a continuous path by a plurality of guiderolls 42. Also included is a pick up roll 44 designed to facilitatetransfer of web 38 from fabric 26 to fabric 40. Preferably, the speed atwhich fabric 40 is driven is approximately the same speed at whichfabric 26 is driven so that movement of web 38 through the system isconsistent.

[0054] From fabric 40, web 38, in this embodiment, is transferred to thesurface of a rotatable heated dryer drum 46, such as a Yankee dryer. Web38 is lightly pressed into engagement with the surface of dryer drum 46to which it adheres, due to its moisture content and its preference forthe smoother of the two surfaces. As web 38 is carried through a portionof the rotational path of the dryer surface, heat is imparted to the webcausing most of the moisture contained within the web to be evaporated.

[0055] In an alternative embodiment, web 38 can be through dried insteadof being placed on a dryer drum. A through dryer accomplishes theremoval of moisture from the web by passing air through the web withoutapplying any mechanical pressure. Through drying can increase the bulkand softness of the web.

[0056] From drier drum 46, as shown in FIG. 2, web 38 is pressed intoengagement with a creping drier 45 by a press roll 43. Press roll 43 incombination with creping drier 45 apply a sufficient amount of heat andpressure to web 38 for causing the web to adhere to the creping driersurface without the use of an adhesive. An adhesive, however, if desiredmay be applied over the surface of the web or drum for facilitatingattachment of the web to the drum.

[0057] Web 38 is then removed from drier drum 45 by a creping blade 47.Creping web 38 as it is formed reduces internal bonding within the weband increases softness.

[0058] The base web formed from the process illustrated in FIG. 2,possesses certain physical characteristics that are particularlyadvantageous for use in the remainder of the process of the presentinvention. In particular, web 38 is characterized by having a reducedamount of inner fiber bonding strength. As described above, the web canalso contain hardwood fibers. Low bonding strength in combination withhardwood fibers provides softness, bulk, absorbency, opacity, wickingability and brightness. As will be described hereinafter, the remainderof the process of the present invention is designed not only to enhancethe above properties but also to provide the paper web with strength andstretchability.

[0059] Once paper web 38 is formed, a bonding material may be applied toat least one side of the web and at least one side of the web may thenbe creped. For most applications, desirably a bonding material isapplied to both sides of the web and both sides of the web are creped.When the base web of the present invention is used in a multi-plylaminate, however, it may be desired to only apply the bonding materialto one side of the web. For instance, when making a two-ply product, twobase webs made according to the present invention may be broughttogether and joined along adjacent surfaces where the bonding materialhas not been applied.

[0060] Referring to FIG. 3, a process for applying a bonding material toboth sides of the web and to creping both sides of the web in accordancewith the present invention is illustrated. As shown, desirably, base web38 made according to the process illustrated in FIG. 2 or according to asimilar process, is passed through a first bonding material applicationstation generally 50. Station 50 may include a nip formed by a smoothrubber press roll 52 and a patterned rotogravure roll 54. Rotogravureroll 54 may be in communication with a reservoir 56 containing a firstbonding material 58. Rotogravure roll 54 applies bonding material 58 toone side of web 38 in a preselected pattern.

[0061] Web 38 is then pressed into contact with a first creping drum 60by a press roll 62. The bonding material causes only those portions ofthe web where it has been disposed to adhere to the creping surface. Ifdesired, creping drum 60 can be heated for promoting attachment betweenthe web and the surface of the drum and for partially drying the web.

[0062] Once adhered to creping drum 60, web 38 may be brought intocontact with a creping blade 64. Specifically, web 38 may be removedfrom creping roll 60 by the action of creping blade 64, performing afirst controlled pattern crepe on the web.

[0063] Once creped, web 38 can be advanced by pull rolls 66 to a secondbonding material application station generally 68. Station 68 mayinclude a transfer roll 70 in contact with a rotogravure roll 72, whichmay be in communication with a reservoir 74 containing a second bondingmaterial 76. Similar to station 50, second bonding material 76 may beapplied to the opposite side of web 38 in a preselected pattern. Oncethe second bonding material is applied, web 38 may be adhered to asecond creping roll 78 by a press roll 80. Desirably, web 38 is carriedon the surface of creping drum 78 for a distance and then removedtherefrom by the action of a second creping blade 82. Second crepingblade 82 performs a second controlled pattern creping operation on thesecond side of the base web.

[0064] Once creped for a second time, base web 38, in this embodiment,is pulled through a curing or drying station 84. Drying station 84 caninclude any form of a heating unit, such as an oven energized byinfrared heat, microwave energy, hot air or the like. Drying station 84may be necessary in some applications to dry the web and/or cure thefirst and second bonding materials. Depending upon the bonding materialsselected, however, in other applications drying station 84 may not beneeded.

[0065] Once drawn through drying station 84, web 38 can be wound into aroll of material 86 for immediate use of for further processingaccording to the present invention.

[0066] The bonding materials applied to each side of base web 38 areselected for not only assisting in creping the web but also for addingdry strength, wet strength, stretchability, and tear resistance to theweb. The bonding materials also prevent lint from escaping from the webduring use.

[0067] The bonding material may be applied to the base web as describedabove in a preselected pattern. In one embodiment, for instance, thebonding agent can be applied to the web in a reticular pattern, suchthat the pattern is interconnected forming a net-like design on thesurface.

[0068] In an alternative embodiment, the bonding material can be appliedto the web in a pattern that represents a succession of dots or othergeometric shapes. Applying the bonding material in discrete shapes, suchas dots, provides strength to the web without covering a substantialportion of the surface area of the web.

[0069] In general, according to the present invention, the bondingmaterial may be applied to each side of the base web so as to cover fromabout 10% to about 60% of the surface area of the web. Moreparticularly, in most applications, the bonding material will cover fromabout 20% to about 50% of the surface area of each side of the web. Theamount of bonding material applied to each side of the web willdesirably be in the range of from about 3% to about 10% by weight andparticularly from about 6% to 8% by weight, based upon the total weightof the web. For instance, in one embodiment, the bonding material can beapplied to each side of the web in an amount of about 7% by weight.

[0070] At the above amounts, the bonding material can penetrate the baseweb from about 25% to about 50% of the total thickness of the web. Inmost applications, the bonding material should at least penetrate fromabout 10% to about 15% of the thickness of the web.

[0071] Particular bonding materials that may be used in the presentinvention include latex compositions, such as acrylates, vinyl acetates,vinyl chlorides, and methacrylates. Some water soluble bonding materialsmay also be used including polyacrylamides, polyvinyl alcohols, andcarboxymethyl cellulose.

[0072] In one preferred embodiment, the bonding material used in theprocess of the present invention comprises an ethylene vinyl acetatecopolymer. In particular, the ethylene vinyl acetate copolymer isdesirably cross-linked with N-methyl acrylamide groups using an acidcatalyst. Suitable acid catalysts include ammonium chloride, citricacid, and maleic acid. The bonding material should have a glasstransition temperature of not lower than −10° F. and not higher than+20° F.

[0073] Base webs made according to the above described process providemany advantages and benefits over conventional constructions. Inparticular, base webs made according to the present invention haveenhanced abrasion resistant properties and tensile strength properties.In fact, it has been discovered that base webs made according to thepresent invention have a total tensile strength (cross direction plusmachine direction strength) that is much higher at higher bulks thanmany prior art constructions. Further, when the base web of the presentinvention contains hardwood fibers or other highly wettable fibers asdescribed above, the strength of the web is enhanced while at the sametime creating a web with good wipe dry properties.

[0074] The basis weight of base webs made according to the presentinvention can vary depending upon the particular application. Ingeneral, for most applications, the basis weight can be from about 20pounds per 2,880 square feet (ream) to about 80 pounds per ream. Some ofthe uses of the base webs include use as a wiping product, as a napkin,as a medical pad, as an absorbent layer in a laminate product, as aplacemat, as a drop cloth, as a cover material, or for any product thatrequires liquid absorbency.

[0075] The present invention may be better understood with reference tothe following example.

EXAMPLE

[0076] The following example was performed in order to compare a baseweb made according to the present invention with a base web that hasbeen used in the past as a wiping product.

[0077] A base web made in accordance with the present invention wasproduced according to a process similar to the one illustrated in FIGS.1-3. The base web contained a middle layer separated by two outerlayers. In particular, each outer layer accounted for about 26% byweight of the web, while the middle layer accounted for about 47% of theweight of the web.

[0078] In accordance with the present invention, each outer layercontained polyester fibers. The polyester fibers were present within theweb in an total amount of about 8% by weight (4% by weight in each outerlayer). In this arrangement, the polyester fibers accounted for about15% of the surface fibers. The remainder of the outer layers wascomprised of pulp fibers, specifically softwood fibers.

[0079] The middle layer contained a mixture of softwood fibers andeucalyptus fibers. The eucalyptus fibers were present in the base web inan amount of 20% by weight, so as to account for about 42% by weight ofthe middle layer.

[0080] After the base web was formed, a bonding material was printed oneach side of the web and both sides of the web were creped. The bondingmaterial used was an ethylene vinyl acetate latex. The bonding materialwas applied to each side of the web according to a small diamond-shapedpattern. The bonding material was also applied to one side of the webaccording to a larger diamond-shaped pattern mostly to improve theaesthetic appearance of the base web.

[0081] In was noticed that the resulting base web had good handfeel anda good aesthetic appearance. Four samples of the base web were testedand the following results were obtained: TABLE 1 Results of a Base Webmade According to the Present Invention Cross Machine Cross DirectionDirection Machine Direction Cross Total Wet Basis Weight TensileDirection Tensile Direction Tensile Tensile Sample (lbs/ream) Bulk(oz/in) Stretch (%) (oz/in) Stretch (%) (oz/in) (oz/in) 1 46.4 33.5 62.633.5 43.5 22.0 106.1 29.6 2 45.9 32.4 64.3 35.9 44.2 20.2 108.5 27.1 347.1 32.9 64.7 33.8 47.3 19.3 112.1 31.1 4 46.1 32.0 66.7 40.0 44.2 22.6110.9 30.0 Total 46.4 32.7 64.6 35.8 44.8 21.0 109.4 29.4 Average

[0082] The above base web was compared to a conventionally mademulti-layered base web containing polyester fibers in the middle layer.In the past, polyester fibers were incorporated into the middle layer ofbase webs in order to increase the strength of the webs.

[0083] The conventionally made base web included two outer layers madefrom softwood fibers and a middle layer containing a mixture of softwoodfibers and polyester fibers. The polyester fibers were present withinthe middle layer in an amount of 15% by weight of the middle layer. Eachlayer of the web accounted for ⅓ of the total weight of the web.

[0084] Similar to the base web described above made according to thepresent invention, a bonding material was applied to each side of theconventionally made web and the web was creped on both sides.

[0085] Five samples of the conventionally made base web were tested andthe results are as follows: TABLE 2 Results of a Conventionally madeBase Web Containing Polyester Fibers in the Middle Layer Cross MachineCross Direction Direction Machine Direction Cross Wet Basis WeightTensile Direction Tensile Direction Tensile Sample (lbs/ream) Bulk(oz/in) Stretch (%) (oz/in) Stretch (%) (oz/in) A 45.8 39.03 51.6 31.246.7 15.8 29 B 46 38.16 52.7 28.8 44.1 14.4 29.5 C 46.8 39.73 56.2 29.145.7 15.1 29.1 D 46 37.96 53.2 30.04 46.5 15.6 28.3 E 46.8 39.03 61.931.8 46.5 15.8 30.1 Average 46.3 38.8 55.1 30.2 45.9 15.3 29.2

[0086] As shown above when comparing the two tables, the base web madeaccording to the present invention had much better machine directiontensile strength and stretch properties than the conventionally madeweb. The total tensile strength of the base web made according to thepresent invention is also much greater in comparison to prior artconstructions, especially at the bulk level that was tested. Further,although the cross direction strength and stretch properties were not asgood as the conventionally made web, the base web of the presentinvention had better strength in the cross direction when wet. Further,because the base web of the present invention contains synthetic fiberson the outer layers, the web should have better abrasion resistantproperties than the conventionally made web.

[0087] These and other modifications and variations to the presentinvention may be practiced by those of ordinary skill in the art,without departing from the spirit and scope of the present invention,which is more particularly set forth in the appended claims. Inaddition, it should be understood that aspects of the variousembodiments may be interchanged both in whole or in part. Furthermore,those of ordinary skill in the art will appreciate that the foregoingdescription is by way of example only, and is not intended to limit theinvention so further described in such appended claims.

What is claimed is:
 1. An abrasion resistant liquid absorbent base webcomprising: a first outer fibrous layer defining a first side of saidbase web and a second and opposing outer fibrous layer defining a secondside of said base web, said first and second outer layers containingsynthetic staple fibers; an intermediate fibrous layer positionedbetween said first outer layer and said second outer layer, saidintermediate layer comprising pulp fibers; a bonding material applied toat least one of said sides of said base web, said bonding material beingapplied to said at least one side according to a predetermined pattern;and wherein said at least one side of said base web is creped after saidbonding material has been applied.
 2. A base web as defined in claim 1,wherein said synthetic stable fibers comprise fibers containingpolyester, nylon, polypropylene, rayon, or mixtures thereof.
 3. A baseweb as defined in claim 1, wherein said synthetic staple fibers have alength of at least 0.25 inches and have a denier of less than about 2.5.4. A base web as defined in claim 1, wherein said synthetic staplefibers are present within said web in an amount up to about 50% byweight.
 5. A base web as defined in claim 1, wherein said first andsecond outer layers further contain pulp fibers combined with saidsynthetic staple fibers.
 6. A base web as defined in claim 1, whereinsaid synthetic staple fibers are present within said web in an amountfrom about 5% to about 15% by weight.
 7. A base web as defined in claim1, wherein said synthetic staple fibers comprise polyester fibers.
 8. Abase web as defined in claim 1, wherein said intermediate layercomprises hardwood fibers having a fiber length of less than about 2millimeters.
 9. A base web as defined in claim 1, wherein a bondingmaterial is applied to said first side of said web and to said secondside of said web and wherein both sides of said web are creped.
 10. Abase web as defined in claim 1, wherein said intermediate layercomprises alpha pulp fibers.
 11. An abrasion resistant liquid absorbentbase web comprising: a first outer fibrous layer defining a first sideof said base web and a second and opposing outer fibrous layer defininga second side of said base web, said first and second outer layerscomprising a mixture of synthetic staple fibers and pulp fibers, saidsynthetic staple fibers containing a material selected from the groupconsisting of polyester, nylon, polypropylene, rayon and mixturesthereof, each of said first and second outer layers comprising fromabout 15% to about 40% by weight of said base web; an intermediatefibrous layer positioned between said first outer layer and said secondouter layer, said intermediate layer comprising fibers having a lengthof less than about 2.0 mm and a coarseness of less than about 10; abonding material applied to at least one side of said base web, saidbonding material being applied to said at least one side according to apreselected pattern; and wherein said at least one side of said base webis creped after said bonding material has been applied.
 12. A base webas defined in claim 11, wherein a bonding material is applied to saidfirst side of said web and to said second side of said web and whereinboth sides of said web are creped.
 13. A base web as defined in claim11, wherein said synthetic staple fibers are present within said baseweb in an amount from about 5% to about 15% by weight.
 14. A base web asdefined in claim 11, wherein said fibers contained within saidintermediate layer comprise eucalyptus fibers or eucalyptus-like fibers.15. A base web as defined in claim 11, wherein said fibers containedwithin said intermediate layer comprise hardwood fibers.
 16. A base webas defined in claim 11, wherein said fibers contained within saidintermediate layer are added in an amount from about 10% to about 40% byweight of said base web.
 17. A base web as defined in claim 11, whereinsaid fibers contained within said intermediate layer are added in anamount sufficient to create a pore size gradient between saidintermediate layer and said first and second outer layers.
 18. A methodfor producing a liquid absorbent base web comprising the steps of:providing a fibrous web including a middle layer comprising hardwoodfibers or alpha pulp fibers, a first outer layer comprising a mixture ofpulp fibers and synthetic staple fibers, and a second outer layer alsocomprising a mixture of pulp fibers and synthetic staple fibers, saidfibrous web having a first side and a second side; applying a firstbonding material to said first side of said web in a preselected patternand adhering said first side of said web to a first creping surface; andcreping said first side of said web from said first creping surface. 19.A method as defined in claim 18, further comprising the steps ofapplying a second bonding material to said second side of said web in apreselected pattern and adhering said second side of said web to asecond creping surface; and creping said second side of said web fromsaid second creping surface.
 20. A method as defined in claim 18,wherein said synthetic staple fibers are present within said web in anamount up to about 50% by weight, said synthetic staple fiberscontaining a material selected from the group consisting of polyester,nylon, polypropylene, rayon and mixtures thereof.
 21. A method asdefined in claim 18, wherein said middle layer comprises a mixture ofpulp fibers and hardwood fibers, said hardwood fibers comprisingeucalyptus fibers or eucalyptus-like fibers.
 22. A method as defined inclaim 19, wherein said first bonding material and said second bondingmaterial are each applied to said base web in an amount up to about 10%by weight, said first and second bonding materials being applied to saidbase web in a pattern that covers from about 20% to about 50% of thesurface area of said first and second sides of said base webrespectively.
 23. A wiping product comprising: a base web including afirst outer fibrous layer defining a first side of said base web and asecond and opposing outer fibrous layer defining a second side of saidbase web, said first and second outer layers comprising a mixture ofsynthetic staple fibers and pulp fibers, said synthetic staple fibersbeing present within said wiping product in an amount from about 5% toabout 15% by weight, each of said first and second outer layerscomprising from about 15% to about 40% of the weight of said base web;an intermediate fibrous layer positioned between said first outer layerand said second outer layer, said intermediate layer comprising hardwoodfibers or alpha pulp fibers, said hardwood fibers or alpha pulp fibersbeing present within said base web in an amount from about 10% to about40% by weight; a bonding material applied to said first side of saidbase web according to a first predetermined pattern and to said secondside of said base web according to a second predetermined pattern; andwherein said first side and said second side of said base web are crepedafter said bonding material has been applied.
 24. A wiping product asdefined in claim 23, wherein said synthetic staple fibers comprisepolyester fibers.
 25. A wiping product as defined in claim 23, whereinsaid intermediate layer comprises hardwood fibers, said hardwood fiberscomprising eucalyptus fibers or eucalyptus-like fibers.
 26. A wipingproduct as defined in claim 25, wherein said intermediate layer furthercontains softwood fibers.